Conventionally, there have been known flow path structures internally including small flow paths into which fluid is introduced. For example, Patent Document 1 listed below teaches a reactor including such a flow path structure.
In the reactor disclosed in Patent Document 1, a plurality of small flow paths is parallelly arranged inside the flow path structure. A first feedstock fluid and a second feedstock fluid are introduced into each flow path from an end thereof. Then, a desired product is prepared by causing the first feedstock fluid and the second feedstock fluid to react with each other while flowing through each flow path toward its outlet side.
Here, when the plurality of flow paths is formed in the flow path structure as described above, it is desired that the flow rate of the fluid flowing through each flow path be equal to each other. For example, in a heat exchanger described in Patent Document 2, a pressure loss in each flow path is equalized among the flow paths by making flow path lengths uniform for each flow path, so that the flow rate of the fluid flowing in the flow path becomes equal to each other.
However, such an attempt of making the flow path lengths uniform for each flow path will pose a severe restriction on shape of each flow path, leading to a problem in that it becomes difficult to freely design the flow path.
Patent Document 1: Published Japanese Translation of Unexamined PCT Patent Application No. 2005-525229
Patent Document 2: Japanese Patent Laid-Open Publication No. S64-3496